1. Field of the Invention
The present invention relates to the refining of vegetable oils and, more particularly, to the dewaxing of crude sunflower seed oil.
2. Description of the Prior Art
New and better sources of food are required to satisfy the needs of expanding world population. Oil seeds such as soybean, sunflower, peanut, cottonseed, rapeseed, sesame and safflower are promising and readily available sources for food. Though the sunflower has been recognized for many years, it has only recently gained an important position in the world food supply and the present production of sunflower seed as a source of oil and protein represents about 10% of the world production of fatty oils. Sunflower oil has some very attractive properties as an edible oil because of its unsaturated, fatty acid composition and it can be cultivated with good yield.
However, sunflower oil contains a significant amount of wax which is difficult to remove and has a tendency to cloud the oil when stored at room or colder temperatures. This wax fraction is unsaponifiable and has a high melting point and low solubility. A cloudy precipitate will be found in refined and bleached oil at refrigerator temperature or even at room temperature if these waxes are not removed from the oil.
The conventional procedure for refining sunflower oil proceeded by a conventional lye refining at 70.degree.-90.degree. C followed by bleaching and then chilling of the oil to a low temperature to precipitate the wax. The waxes are then removed by filtration and the oil is deodorized. The filtration is a difficult, slow and expensive process requiring large filtering capacity and high labor requirements.
A recently proposed method for dewaxing sunflower oil which proceeded by treatment of crude sunflower seed oil with certain surfactants in combination with degumming agents was found to remove approximately 80% of the waxes. However, this oil is still commercially unacceptable since it is found to cloud when stored at room temperature and especially when placed in a chilled refrigerated environment.